// https://github.com/PrismJS/prism/blob/master/plugins/diff-highlight/prism-diff-highlight.js
module.exports = (Prism) => {
  var LANGUAGE_REGEX = /diff-([\w-]+)/i
  var HTML_TAG = /<\/?(?!\d)[^\s>\/=$<%]+(?:\s(?:\s*[^\s>\/=]+(?:\s*=\s*(?:"[^"]*"|'[^']*'|[^\s'">=]+(?=[\s>]))|(?=[\s/>])))+)?\s*\/?>/gi
  //this will match a line plus the line break while ignoring the line breaks HTML tags may contain.
  var HTML_LINE = RegExp(
    /(?:__|[^\r\n<])*(?:\r\n?|\n|(?:__|[^\r\n<])(?![^\r\n]))/.source.replace(/__/g, function () {
      return HTML_TAG.source
    }),
    'gi'
  )

  var PREFIXES = Prism.languages.diff.PREFIXES

  Prism.hooks.add('before-sanity-check', function (env) {
    var lang = env.language
    if (LANGUAGE_REGEX.test(lang) && !env.grammar) {
      env.grammar = Prism.languages[lang] = Prism.languages['diff']
    }
  })
  Prism.hooks.add('before-tokenize', function (env) {
    var lang = env.language
    if (LANGUAGE_REGEX.test(lang) && !Prism.languages[lang]) {
      Prism.languages[lang] = Prism.languages['diff']
    }
  })

  Prism.hooks.add('wrap', function (env) {
    var diffLanguage, diffGrammar

    if (env.language !== 'diff') {
      var langMatch = LANGUAGE_REGEX.exec(env.language)
      if (!langMatch) {
        return // not a language specific diff
      }

      diffLanguage = langMatch[1]
      diffGrammar = Prism.languages[diffLanguage]
    }

    // one of the diff tokens without any nested tokens
    if (env.type in PREFIXES) {
      /** @type {string} */
      var content = env.content.replace(HTML_TAG, '') // remove all HTML tags

      /** @type {string} */
      var decoded = content.replace(/&lt;/g, '<').replace(/&amp;/g, '&')

      // remove any one-character prefix
      var code = decoded.replace(/(^|[\r\n])./g, '$1')

      // highlight, if possible
      var highlighted
      if (diffGrammar) {
        highlighted = Prism.highlight(code, diffGrammar, diffLanguage)
      } else {
        highlighted = Prism.util.encode(code)
      }

      // get the HTML source of the prefix token
      var prefixToken = new Prism.Token('prefix', PREFIXES[env.type], [/\w+/.exec(env.type)[0]])
      var prefix = Prism.Token.stringify(prefixToken, env.language)

      // add prefix
      var lines = [],
        m
      HTML_LINE.lastIndex = 0
      while ((m = HTML_LINE.exec(highlighted))) {
        lines.push(prefix + m[0])
      }
      if (/(?:^|[\r\n]).$/.test(decoded)) {
        // because both "+a\n+" and "+a\n" will map to "a\n" after the line prefixes are removed
        lines.push(prefix)
      }
      env.content = lines.join('')

      if (diffGrammar) {
        env.classes.push('language-' + diffLanguage)
      }
    }
  })
}
